.. image:: ./documentation/assets/github-banner.png




--------




#############################################
kawipiko -- blazingly fast static HTTP server
#############################################




.. highlights::

    Table of contents:

    * `Manual <#manual>`__ and `Examples <#examples>`__
    * `Installation <#installation>`__ and `FAQ <#faq>`__
    * `Features <#features>`__ and `Benchmarks <#benchmarks>`__
    * `About <#about>`__, `Copyright and licensing <#notice-copyright-and-licensing>`__, `SBOM <#sbom-software-bill-of-materials>`__, and `References <#references>`__
    * `chat on Discord <https://discord.gg/NH7V7NKjNu>`__, `discuss on GitHub <https://github.com/volution/kawipiko/discussions/categories/discussions>`__, or `email author <mailto:ciprian.craciun@gmail.com>`__




--------




About
=====


``kawipiko`` is a **lightweight static HTTP server** written in Go;
focused on serving static content **as fast and efficient as possible**,
with the **lowest latency**, and with the lowest resource consumption (either CPU, RAM, IO);
supporting both **HTTP/1 (with or without TLS), HTTP/2 and HTTP/3 (over QUIC)**;
available as a **single statically linked executable** without any other dependencies.


Want to see ``kawipiko`` in action?

* `kawipiko-examples.volution.ro <https://kawipiko-examples.volution.ro/>`__
  -- here are a few demos that best fit `kawipiko`;
  ``/documentation`` represents static sites that compress well,
  meanwhile ``/carina-nebula``, ``/openstreetmap`` and ``/fontawesome`` represents static sites that generate lots of small requests;
  (please note that this instance is behind CloudFlare, however it was instructed not to cache anything on the edge;)
  (the server is currently hosted over a residential fiber connection;)

* `notes.volution.ro <https://notes.volution.ro/>`__
  -- my personal notes / blog site, previously hosted at Netlify;
  (the server is currently hosted over a residential fiber connection;)


However, *simple* doesn't imply *dumb* or *limited*,
instead it implies *efficient* through the removal of superfluous features,
thus being inline with UNIX's old philosophy of
"`do one thing and do it well <https://en.wikipedia.org/wiki/Unix_philosophy#Do_One_Thing_and_Do_It_Well>`__".
Therefore, it supports only ``GET`` requests,
and does not provide features like dynamic content generation, authentication, reverse proxying, etc.;
meanwhile still providing compression (``gzip``, ``zopfli``, or ``brotli``),
plus HTML-CSS-JS minifying (TODO),
without affecting its performance
(due to its unique architecture as described below).


What ``kawipiko`` does provide is something very unique, that no other HTTP server offers:
the static content is served from a `CDB file <#why-cdb>`__ with almost no latency
(as compared to classical static servers that still have to pass through the OS via the ``open-read-close`` syscalls).
Moreover, as noted earlier, the static content can still be compressed or minified ahead of time,
thus reducing not only CPU but also bandwidth and latency.


`CDB files <#why-cdb>`__ are binary database files that provide efficient read-only key-value lookup tables,
initially used in some DNS and SMTP servers,
mainly for their low overhead lookup operations,
zero locking in multi-threaded / multi-process scenarios,
and "atomic" multi-record updates.
This also makes them suitable for low-latency static content serving over HTTP,
which is what this project provides.


For those familiar with Netlify (or competitors like CloudFlare Pages, GitHub Pages, etc.),
``kawipiko`` is a *host-it-yourself* alternative featuring:

* self-contained deployment with simple configuration;
  (i.e. just `fetch the executable <#installation>`__ and use the `proper flags <#kawipiko-server>`__;)

* low and constant resource consumption (both in terms of CPU and RAM);
  (i.e. you won't have surprises when under load;)

* (hopefully) extremely secure;
  (i.e. it doesn't launch processes, it doesn't connect to other services or databases, it doesn't open any files, etc.;
  basically you can easily ``chroot`` it, or containerize it as is in fashion these days;)

* highly portable, supporting at least Linux (the main development, testing and deployment platform), FreeBSD, OpenBSD, and OSX;


For a complete list of features please consult the `features section <#features>`__.
Unfortunately, there are also some tradeoffs as described in the `limitations section <#limitations>`__
(although none are critical).


With regard to performance, as described in the `benchmarks section <#benchmarks>`__,
``kawipiko`` is at least on-par with NGinx,
sustaining over 100K requests / second with 0.25ms latency for 99% of the requests even on my 6 years old laptop.
However the main advantage over NGinx is not raw performance,
but deployment and configuration simplicity,
plus efficient management and storage of large collections of many small files.


In relation to ``kawipiko`` I've also published a few articles on my own site:

* `Securing my static site server with seccomp <https://notes.volution.ro/v1/2022/09/remarks/794866f7/>`__
  -- describes how I have employed Linux's ``seccomp`` syscall filtering to improve the security by reducing the attack surface;
* `Static site hosting hurdres <https://notes.volution.ro/v1/2022/09/notes/b08118d8/>`__
  -- describes the reasoning behind implementing this simple HTTP server;
* `A visual comparison between HTTP/1.1 and HTTP/2 <https://notes.volution.ro/v1/2019/08/notes/e8700e9a/>`__
  -- a few experiments in how Firefox and Chromium handle lots of resource loading over HTTP/1.1 vs HTTP/2;
  (the server used for the expermients was ``kawipiko``;)




--------




Manual
======

.. contents::
    :local:
    :backlinks: none




Workflow
--------


The project provides the following executables (statically linked, without any other dependencies):

* ``kawipiko-server`` -- which serves the static content from the CDB archive either via HTTP (with or without TLS), HTTP/2 or HTTP/3 (over QUIC);

* ``kawipiko-archiver`` -- which creates the CDB archive from a source folder holding the static content,
  optionally compressing and minifying files;

* ``kawipiko`` -- an all-in-one executable that bundles all functionality in one executable;
  (i.e. ``kawipiko server ...`` or ``kawipiko archiver ...``);


Unlike most (if not all) other servers out-there,
in which you just point your web server to the folder holding the static website content root,
``kawipiko`` takes a radically different approach:
in order to serve the static content,
one has to first *archive* the content into the CDB archive through ``kawipiko-archiver``,
and then one can *serve* it from the CDB archive through ``kawipiko-server``.


This two step phase also presents a few opportunities:

* one can decouple the "building", "testing", and "publishing" phases of a static website,
  by using a similar CI/CD pipeline as done for other software projects;

* one can instantaneously rollback to a previous version if the newly published one has issues;

* one can apply extreme compression (e.g. ``zopfli`` or ``brotli``),
  to trade CPU during deployment vs latency and bandwidth at runtime.




kawipiko-server
---------------


See the `dedicated manual <./documentation/manuals/server.rst>`__.

This document is also available
in `plain text <./documentation/manuals/server.txt>`__,
or as a `man page <./documentation/manuals/server.1.man>`__.




kawipiko-archiver
-----------------


See the `dedicated manual <./documentation/manuals/archiver.rst>`__.

This document is also available
in `plain text <./documentation/manuals/archiver.txt>`__,
or as a `man page <./documentation/manuals/archiver.1.man>`__.




--------




Examples
========


* fetch and extract the Python 3.10 documentation HTML archive: ::

    curl \
            -s -S -f \
            -o ./python-3.10.1-docs-html.tar.bz2 \
            https://docs.python.org/3/archives/python-3.10.1-docs-html.tar.bz2 \
    #

    tar \
            -x -j -v \
            -f ./python-3.10.1-docs-html.tar.bz2 \
    #


* create the CDB archive (without any compression): ::

    kawipiko-archiver \
            --archive ./python-3.10.1-docs-html-nocomp.cdb \
            --sources ./python-3.10.1-docs-html \
            --debug \
    #


* create the CDB archive (with ``gzip`` compression): ::

    kawipiko-archiver \
            --archive ./python-3.10.1-docs-html-gzip.cdb \
            --sources ./python-3.10.1-docs-html \
            --compress gzip \
            --debug \
    #


* create the CDB archive (with ``zopfli`` compression): ::

    kawipiko-archiver \
            --archive ./python-3.10.1-docs-html-zopfli.cdb \
            --sources ./python-3.10.1-docs-html \
            --compress zopfli \
            --debug \
    #


* create the CDB archive (with ``brotli`` compression): ::

    kawipiko-archiver \
            --archive ./python-3.10.1-docs-html-brotli.cdb \
            --sources ./python-3.10.1-docs-html \
            --compress brotli \
            --debug \
    #


* serve the CDB archive (with ``gzip`` compression): ::

    kawipiko-server \
            --bind 127.0.0.1:8080 \
            --archive ./python-3.10.1-docs-html-gzip.cdb \
            --archive-mmap \
            --archive-preload \
            --debug \
    #


* compare sources and archive sizes: ::

    du \
            -h -s \
            \
            ./python-3.10.1-docs-html-nocomp.cdb \
            ./python-3.10.1-docs-html-gzip.cdb \
            ./python-3.10.1-docs-html-zopfli.cdb \
            ./python-3.10.1-docs-html-brotli.cdb \
            \
            ./python-3.10.1-docs-html \
            ./python-3.10.1-docs-html.tar.bz2 \
    #

    45M     ./python-3.10.1-docs-html-nocomp.cdb
    9.7M    ./python-3.10.1-docs-html-gzip.cdb
    ???     ./python-3.10.1-docs-html-zopfli.cdb
    7.9M    ./python-3.10.1-docs-html-brotli.cdb

    46M     ./python-3.10.1-docs-html
    6.0M    ./python-3.10.1-docs-html.tar.bz2




--------




Installation
============


See the `dedicated installation document <./documentation/readme/installation.rst>`__.




--------




Features
========

.. contents::
    :local:
    :backlinks: none




Implemented
-----------


The following is a list of the most important features:

* (optionally)  the static content is compressed or minified when the CDB archive is created,
  thus no CPU cycles are used while serving requests;

* (optionally)  the static content can be compressed with either ``gzip``, ``zopfli`` or ``brotli``;

* (optionally)  in order to reduce the serving latency even further,
  one can preload the entire CDB archive in memory, or alternatively mapping it in memory (using ``mmap``);
  this trades memory for CPU;

* (optionally)  caching the static content fingerprint and compression,
  thus significantly reducing the CDB archive rebuilding time,
  and significantly reducing the IO for the source file-system;

* atomic static website content changes;
  because the entire content is held in a single CDB archive,
  and because the file replacement is atomically achieved via the ``rename`` syscall (or the ``mv`` tool),
  all served resources are observed to change at the same time;

* ``_wildcard.*`` files (where ``.*`` are the regular extensions like ``.txt``, ``.html``, etc.)
  which will be used if an actual resource is not found under that folder;
  (these files respect the hierarchical tree structure, i.e. "deeper" ones override the ones closer to "root";)

* support for HTTP/1 (with or without TLS), by leveraging ``github.com/valyala/fasthttp``;

* support for HTTP/2, by leveraging Go's ``net/http``;

* support for HTTP/3 (over QUIC), by leveraging ``github.com/lucas-clemente/quic-go``;




Pending
-------


The following is a list of the most important features that are currently missing and are planed to be implemented:

* (TODO)  support for custom HTTP response headers (for specific files, for specific folders, etc.);
  (currently only ``Content-Type``, ``Content-Length``, ``Content-Encoding`` are included;
  additionally ``Cache-Control: public, immutable, max-age=3600``, optionally ``ETag``,
  and a few TLS or security related headers can also be included;)

* (TODO)  support for mapping virtual hosts to key prefixes;
  (currently virtual hosts, i.e. the ``Host`` header, is supported by the server, and partially by the archiver;)

* (TODO)  support for mapping virtual hosts to multiple CDB archives;
  (i.e. the ability to serve multiple domains, each with its own CDB archive;)

* (TODO)  automatic reloading of the CDB archives;

* (TODO)  minifying HTML, CSS and JavaScript, by leveraging ``https://github.com/tdewolff/minify``;

* (TODO)  customized error pages (embedded in the CDB archive);
  (currently only ``404`` wildcards are supported;)




Limitations
-----------


As stated in the `about section <#about>`__, nothing comes for free,
and in order to provide all these features, some corners had to be cut:

* (TODO)  currently if the CDB archive changes,
  the server needs to be restarted in order to pickup the changed files;

* (won't fix)  the CDB archive **maximum size is 4 GiB** (after compression and minifying),
  and there can't be more than 16M resources;
  (however if you have a static website this large,
  you are probably doing something extremely wrong,
  as large files should be offloaded to something like AWS S3,
  and served through a CDN like CloudFlare or AWS CloudFront;)

* (won't fix)  the server **does not support per-request decompression / recompression**;
  this implies that if the content was saved in the CDB archive with compression (say ``brotli``),
  the server will serve all resources compressed (i.e. ``Content-Encoding: brotli``),
  regardless of what the browser accepts (i.e. ``Accept-Encoding: gzip``);
  the same applies for uncompressed content;
  (however always using ``gzip`` compression is safe enough,
  as it is implemented in virtually all browsers and HTTP clients out there;)

* (won't fix)  regarding the "atomic" static website changes,
  there is a small time window in which a client that has fetched an "old" version of a resource (say an HTML page),
  but it has not yet fetched the required resources (say the CSS or JS files),
  and in between fetching the HTML and CSS/JS the CDB archive was changed,
  the client will consequently fetch the new version of these required resources;
  however due to the low latency serving, this time window is extremely small;
  (**this is not a limitation of this HTTP server, but a limitation of the way websites are built;**
  always use fingerprints in your resources URL,
  and perhaps always include the current and previous version on each deploy;)




--------




Benchmarks
==========


See the `dedicated benchmarks document <./documentation/readme/benchmarks.rst>`__.




--------




FAQ
===




How to ask for help?
--------------------

If you have encountered a bug,
just use the `GitHub issues <https://github.com/volution/kawipiko/issues>`__.

If you are not sure about something,
want to give feedback,
or request new features,
just use the `GitHub discussions <https://github.com/volution/kawipiko/discussions/categories/discussions>`__.

If you want to ask a quick question,
or just have a quick chat,
just head over to the `Discord channel <https://discord.gg/NH7V7NKjNu>`__.




Is it production ready?
-----------------------


Yes, it currently is serving ~600K HTML pages.


Although, being open source, you are responsible for making sure it works within your requirements!


However, I am available for consulting on its deployment and usage.  :)




Why CDB?
--------


CDB is the venerable key-value embedded database implemented by D.J. Bernstein, `<https://cr.yp.to/cdb.html>`__,
and was used in many software solutions implemented by him,
most notably `qmail <https://cr.yp.to/qmail.html>`__ and `tinydns <https://cr.yp.to/djbdns/tinydns.html>`__.
From there it was picked up by many other network services that required mostly-static low-overhead lookup tables,
like for example Postfix as an alternative for its user database.

Until I expand upon why I have chosen to use CDB for service static website content,
you can read about the `sparkey <https://github.com/spotify/sparkey>`__ from Spotify.

The CDB implementation being used is a custom fork of the following:

* `github.com/colinmarc/cdb <https://github.com/colinmarc/cdb>`__
  -- the original CDB implementation for Go;

* `github.com/cipriancraciun/go-cdb-lib <https://github.com/cipriancraciun/go-cdb-lib>`__
  -- my own custom fork of the above;
  (it adds support for memory-mapped CDB files,
  plus a few changes to improve performance by making sure that key `[]byte` slices don't "escape to the heap" as required by the Go compiler;)




Why Go?
-------


Because Go is highly portable, highly stable,
and especially because it can easily support cross-compiling statically linked binaries
to any platform it supports.




Why not Rust?
-------------


Because Rust fails to easily support cross-compiling (statically or dynamically linked) executables
to any platform it supports.


Because Rust is less portable than Go;
for example Rust doesn't consider OpenBSD as a "tier-1" platform.




--------




Notice (copyright and licensing)
================================

.. contents::
    :local:
    :backlinks: none




Authors
-------


Ciprian Dorin Craciun
  * `ciprian@volution.ro <mailto:ciprian@volution.ro>`__
    or `ciprian.craciun@gmail.com <mailto:ciprian.craciun@gmail.com>`__
  * `<https://volution.ro/ciprian>`__
  * `<https://github.com/volution>`__
  * `<https://github.com/cipriancraciun>`__

Please also see the `SBOM (Software Bill of Materials) <./documentation/sbom/sbom.md>`__
for links this project's dependencies and their authors.




Notice -- short version
-----------------------


The code is licensed under AGPL 3 or later.


If you **change** the code within this repository **and use** it for **non-personal** purposes,
you'll have to release it as per AGPL.




Notice -- long version
----------------------


For details about the copyright and licensing,
please consult the `notice <./documentation/licensing/notice.txt>`__ file
in the `documentation/licensing <./documentation/licensing>`__ folder.


If someone requires the sources and/or documentation to be released
under a different license, please send an email to the authors,
stating the licensing requirements, accompanied with the reasons
and other details; then, depending on the situation, the authors might
release the sources and/or documentation under a different license.




--------




SBOM (Software Bill of Materials)
=================================


This project, like many other open-source projects,
incorporates code from other open-source projects
(besides other tools used to develop, build and test).

Strictly related to the project's dependencies (direct and transitive),
please see the `SBOM (Software Bill of Materials) <./documentation/sbom/sbom.md>`__
for links to these dependencies and their licenses.




--------




References
==========


See the `dedicated references document <./documentation/readme/references.rst>`__.